This invention relates to reflector lamps and more particularly reflector lamps in which the light source is a tungsten-halogen lamp.
Incandescent reflector lamps are well known. This type of lamp comprises an outer lamp envelope, part of which is a reflector surface for reflecting light incident thereon, and an incandescent filament within the outer envelope. The incandescent filament is positioned relative to the reflector surface for illuminating it during lamp operation. The light from the incandescent filament that is incident on the reflector surface is reflected out of the lamp.
A comparatively recent development is the use of a small tungsten-halogen electric lamp as the light source within a reflector lamp. This allows the lamp to have the higher efficacy, higher color temperature and improved maintenance of tungsten-halogen lamps and at the same time have the directional characteristics and light concentrating properties of reflector lamps.
The incorporation of tungsten-halogen lamps into reflector outer envelopes presents size problems, particularly in smaller lamps. Small reflector lamps do not have sufficient depth to easily accommodate the tungsten-halogen lamp, and mechanical interference between the tungsten-halogen lamp and the outer envelope can be a limitation on the size of the reflector lamp.
One solution to the size problem in small reflector lamps has been to make the lens end of the lamp envelope protrude further forward in order to increase the depth of the lamp interior. This permits the tungsten-halogen lamp to be mounted inside the reflector lamp outer envelope, together with associated parts such as a light shield, without any interference with the lamp outer envelope.
It is known to use a diffusing lens in a reflector lamp in order to broaden the light distribution pattern. A lens having stippling or other surface features will cause the light passing through it to become more diffuse. The beam of light from a reflector lamp will be broader the greater the degree of diffusion that is caused by the lamp lens. By using lamp lenses of different degrees of diffusivity, in lamps that are otherwise identical, lamps having different beam widths can be realized.
The lens surface features which define its diffusing properties are permanently molded in the lens in the course of manufacture. Therefore, lenses having different diffusing properties require different molds, even if they are identical in shape and nominal dimensions. The molds are expensive.
Accordingly, it is an object of the invention to provide a reflector lamp design in which the beam width can be increased without any change to the lens design.
It is another object of the invention to provide a narrow spot reflector lamp made of stock components and which uses a tungsten-halogen incandescent lamp as a light source.